ZrO_2-Al_2O_3复合载体负载Ni基催化剂CO_x甲烷化性能
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摘要
采用浸渍和粉末压片的方法制备了两种ZrO_2-Al_2O_3复合载体并用于负载Ni基催化剂,并利用氮气等温物理吸附、X射线粉末衍射(XRD)、H_2程序升温还原(H_2-TPR)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等分析手段对催化剂物化性质进行表征,考察了ZrO_2-Al_2O_3复合载体制备方法及ZrO_2的引入对Ni基催化剂在CO、CO_2和CO-CO_2共存的3种体系下甲烷化反应活性的影响。材料表征和活性测试结果表明,在CO甲烷化体系中,与单一Al_2O_3载体相比,引入ZrO_2的复合载体能有效提高催化剂中Ni物种的分散度从而增强CO甲烷化过程中催化剂活性,且粉末压片法较浸渍法制备的复合载体能有效提高催化剂的还原度,降低还原温度,但前者会大大降低催化剂的比表面积;在CO_2甲烷化体系中,当载体形貌和制备方法相同时,载体的变化对催化剂活性的影响较小,CO_2转化率主要受到制备方法不同引起的物理性质如比表面积变化的影响;在CO-CO_2共存体系中,由于CO在竞争吸附中比CO_2更容易占据活性位点,所以呈现出优先进行CO甲烷化再进行CO_2甲烷化、CO_2的含量先增多后减少的规律。
Two kinds of nickel-based catalysts supported on ZrO_2-Al_2O_3 composite were prepared by impregnation and powder pressing. The obtained catalysts were further characterized by N_2 isothermal physisorption, X-ray powder diffraction(XRD), H_2 temperature-programmed reduction(H_2-TPR),scanning electron microscope(SEM) and transmission electron microscope(TEM) techniques. The influences of zirconia addition and different preparation methods on the performance of the catalysts in CO methanation, CO_2 methanation and CO/CO_2 co-methanation were investigated. The results indicated that the addition of zirconia in the Al_2O_3 support could improve the dispersion of Ni species, leading to enhanced catalytic performance in CO methanation. Besides, the composite support made from powder pressing method could effectively improve the reducibility and decrease the reduction temperature of catalysts in contrast to that made from the impregnation method. However, the former method would decrease the specific surface area, pore volume and pore diameter of the catalysts. In the CO_2 methanation, catalysts prepared by the same method had little effect on CO_2 conversion, which was mainly limited by the physical properties of the catalysts such as specific surface area that originated from the difference in preparation method. In the CO/CO_2 co-methanation experiments, the methanation of CO is prior to that of CO_2 since in adsorption CO is more easily to occupy the on active sites than CO_2, which causes the CO_2 content increased first and then decreased.
Two kinds of nickel-based catalysts supported on ZrO_2-Al_2O_3 composite were prepared by impregnation and powder pressing. The obtained catalysts were further characterized by N_2 isothermal physisorption, X-ray powder diffraction(XRD), H_2 temperature-programmed reduction(H_2-TPR),scanning electron microscope(SEM) and transmission electron microscope(TEM) techniques. The influences of zirconia addition and different preparation methods on the performance of the catalysts in CO methanation, CO_2 methanation and CO/CO_2 co-methanation were investigated. The results indicated that the addition of zirconia in the Al_2O_3 support could improve the dispersion of Ni species, leading to enhanced catalytic performance in CO methanation. Besides, the composite support made from powder pressing method could effectively improve the reducibility and decrease the reduction temperature of catalysts in contrast to that made from the impregnation method. However, the former method would decrease the specific surface area, pore volume and pore diameter of the catalysts. In the CO_2 methanation, catalysts prepared by the same method had little effect on CO_2 conversion, which was mainly limited by the physical properties of the catalysts such as specific surface area that originated from the difference in preparation method. In the CO/CO_2 co-methanation experiments, the methanation of CO is prior to that of CO_2 since in adsorption CO is more easily to occupy the on active sites than CO_2, which causes the CO_2 content increased first and then decreased.
引文
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[17] LU H, YANG X, GAO G, et al. Mesoporous zirconia-modified clays supported nickel catalysts for CO and CO2methanation[J]. Int. J.Hydrogen Energy, 2014,39(33):18894-18907.
[18] GUO C, WU Y, QIN H, et al. CO methanation over ZrO2/Al2O3supported Ni catalysts:a comprehensive study[J]. Fuel Process Technol, 2014,124:61-69.
[19] HOU Zhaoyin, GAO Jing, GUO Jianzhong, et al. Deactivation of Ni catalysts during methane autothermal reforming with CO2and O2in a fluidized-bed reactor[J]. Journal of Catalysis, 2007, 250(2):331-341.
[20] KATTEL S, YU W, YANG X, et al. CO2Hydrogenation over oxidesupported PtCo catalysts:the role of the oxide support in determining the product selectivity[J]. Angew. Chem.:Int. Ed., 2016, 55:7968-7973.
[21] CHOUDHURY M B I, AHMED S, SHALABI M A, et al. Preferential methanation of CO in a syngas involving CO2at lower temperature range[J]. Applied Catalysis A:General, 2006, 314(1):47-53.
[2] CHEN Min, YANG Xudong. Situations and challenges of household energy consumption in Chinese small towns[J]. Energy and Buildings,2015, 107:155-162.
[3]中华人民共和国国家发展和改革委员会. 2017年天然气行业运行简况[EB/OL].[2018-01-31]. http://www. ndrc. gov. cn/fzgggz/jjyx/mtzhgl/201801/t20180131_876398.html.National Development and Reform Commission. Brief overview of natural gas industry in 2017[EB/OL].http://www.ndrc.gov.cn/fzgggz/jjyx/mtzhgl/201801/t20180131_876398.html.
[4]中华人民共和国国家质量监督检验检疫总局,中国国家标准化管理委员会.人工煤气,GB/T13612—2006[S].北京:中国标准出版社,2007-03-01.General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China, Standardization Administration of the People’S Republic of China. Manufactured gas,GB/T13612—2006[S]. Beijing:Standards Press of China, 2007-03-01.
[5] The Intergovernmental Panel on Climate Change. Carbon dioxide capture and storage[R]. Geneva:IPCC, 2007-09-22.
[6] ABE T, TANIZAWA M, WATANABE K, et al. CO2methanation property of Ru nanoparticle-loaded TiO2prepared by a polygonal barrel-sputtering method[J]. Energy&Environmental Science, 2009, 3(2):315-321.
[7] KANG S, RYU J, KIM J, et al. Co-methanation of CO and CO2on the Ni(X)-Fe(1-X)/Al2O3catalysts:effect of Fe contents[J]. Korean Journal of Chemical Engneering, 2011,12(28):2282-2286.
[8] SRISAWAD N, CHAITREE W, MEKASUWANDUMRONG O, et al.CO2hydrogenation over Co/Al2O3catalysts prepared via a solid-state reaction of fine gibbsite and cobalt precursors[J]. Reaction Kinetics Mechanisms and Catalysis, 2012, 107(1):179-188.
[9] COENEN J W E, VANNISSELROOY P F M T, DECROON M H J M,et al. The dynamics of methanation of carbon monoxide on nickel catalysts[J]. Applied Catalysis, 1986, 25(1/2):1-8.
[10] FUJITA S, TERUNUMA H, NAKAMURA M, et al. Mechanisms of methanation of CO and CO2 over Ni[J]. Industrial&Engineering Chemistry Research, 1991, 30(6):1146-1151.
[11] CAI M, WEN J, CHU W, et al. Methanation of carbon dioxide on Ni/ZrO2-Al2O3catalysts:effects of ZrO2promoter and preparation method of novel ZrO2-Al2O3carrier[J]. Journal of Natural Gas Chemistry,2011, 20(3):318-324.
[12]李凝,罗来涛,欧阳燕.纳米ZrO2/Al2O3复合载体及Ni/ZrO2/Al2O3催化性能的研究[J].催化学报, 2005, 26(9):775-779.LI Ning, LUO Laitao, OUYANG Yan. Studies on properties of nanosized ZrO2/Al2O3composite support and Ni/ZrO2/Al2O3catalyst[J].Chinese Journal of Catalysis, 2005, 26(9):775-779.
[13]杨霞,田大勇,孙守理,等. ZrO2-Al2O3复合载体对镍基催化剂甲烷化性能的影响[J].化工进展, 2014, 33(3):673-678.YANG Xia, TIAN Dayong, SUN Shouli, et al. Influence of zirconiaalumina composite on catalytic performance of nickel-based catalysts for methanation[J]. Chemical Industry and Engineering Progress, 2014,33(3):673-678.
[14] WANG Y, WU R, ZHAO Y. Effect of ZrO2promoter on structure and catalytic activity of the Ni/SiO2catalyst for CO methanation in hydrogen-rich gases[J]. Catalysis Today, 2010, 158(3/4):470-474.
[15] AMAIRIA C, FESSI S, GHORBEL A, et al. Methane oxidation behaviour over sol-gel derived Pd/Al2O3-ZrO2materials:influence of the zirconium precursor[J]. Journal of Molecular Catalysis A:Chemical, 2010, 332(1/2):25-31.
[16] ZHANG J, XU H, JIN X, et al. Characterizations and activities of the nano-sized Ni/Al2O3and Ni/La-Al2O3catalysts for NH3decomposition[J]. Applied Catalysis A:General, 2005, 290(1/2):87-96.
[17] LU H, YANG X, GAO G, et al. Mesoporous zirconia-modified clays supported nickel catalysts for CO and CO2methanation[J]. Int. J.Hydrogen Energy, 2014,39(33):18894-18907.
[18] GUO C, WU Y, QIN H, et al. CO methanation over ZrO2/Al2O3supported Ni catalysts:a comprehensive study[J]. Fuel Process Technol, 2014,124:61-69.
[19] HOU Zhaoyin, GAO Jing, GUO Jianzhong, et al. Deactivation of Ni catalysts during methane autothermal reforming with CO2and O2in a fluidized-bed reactor[J]. Journal of Catalysis, 2007, 250(2):331-341.
[20] KATTEL S, YU W, YANG X, et al. CO2Hydrogenation over oxidesupported PtCo catalysts:the role of the oxide support in determining the product selectivity[J]. Angew. Chem.:Int. Ed., 2016, 55:7968-7973.
[21] CHOUDHURY M B I, AHMED S, SHALABI M A, et al. Preferential methanation of CO in a syngas involving CO2at lower temperature range[J]. Applied Catalysis A:General, 2006, 314(1):47-53.